This invention relates to a process for chemically modifying textile articles which contain hydrolizable polymers to reduce pilling tendency.
Hydrolizable polymers, such as polyester, possess many attributes that lead to their use for many items of commerce, such as fibers, films and molded products. Among these attributes are strength and toughness of the products, lack of reactive surface groups that can lead to staining, and various other advantages. However, many of these attributes can become problematic for certain end uses of the polymers. For example, the tenacity and other strength properties of the hydrolizable polymers such as polyester contribute to their outstanding performance as textile fibers and various other applications, such as films. However, this same strength characteristic can result in a phenomenon known as pilling if this fiber is manufactured, for example, into a spun yarn or in the manufacture of certain microdenier yarns.
Pilling results from fibers being pulled out of the fiber bundle and becoming entangled into a “ball” due to mechanical action, such as rubbing that, for example, fabrics encounter during normal use. Fabrics composed of cellulosic fibers experience similar action, but because the fiber is much weaker, the “pill balls” tend to break off before they become objectionable. These “pill balls” are a detriment to the appearance and comfort of textile articles. Reducing or eliminating the pilling propensity of hydrolizable polymer-containing textile articles would typically extend the useful life of the end-use product, such as a garment, by retaining its original appearance and comfort. Various products introduced by the fiber producers, such as low pill T-351 Trevira® polyester fiber from Hoechst-Celanese, have resulted in some degree of success in reducing pilling tendency. U.S. Pat. No. 3,104,450 to E.I. du Pont de Nemours and Company suggests that by controlling the relative viscosity and the break elongation of polyester fibers, one can reduce the pilling tendency of fabrics containing those spun polyester yarns.
Two major disadvantages are typically associated with fiber modifications made by the fiber producers in attempting to resolve the pilling issue. First, if the fiber producer lowers the fiber strength to the level required for good resistance to pilling, it becomes difficult for the yarn manufacturer to spin the yarn without excessive breaks and resulting off-quality. This necessitates further treatment to adequately reduce the yarn strength, such as alkaline hydrolysis after fabric formation or in a subsequent laundering step, to provide good resistance to pilling. Second, due to the vast number of fiber options (such as denier, cross-section, staple length, etc.) desired in the market, the fiber producer experiences cost, quality, and capacity issues associated with the spinning of small quantities of specialty fibers.
Textile manufacturers face a multitude of challenges in attempting to resolve the pilling issue on textile articles containing hydrolizable polymers. For example, textile chemists have applied binders to increase the force required to remove fibers from the fiber bundle; however, this typically results in detrimental changes to the feel of a fabric, and the effect is generally reduced by washing the fabric or end-use product (i.e. a garment). Some effort has been devoted to lowering the fiber strength by various chemical treatments. Hydrolysis with, for instance, sodium hydroxide does indeed lower the fiber strength, but it is difficult to precisely control this process and the resulting fabric also undergoes a significant weight loss. Aminolysis of the ester linkage of the polymer, such as addressed by Farmer in commonly-assigned U.S. Pat. No. 4,103,051, incorporated by reference herein, indeed can achieve the desired properties in many instances, but also can adversely affect the dyeing of the resulting fabric. This disadvantage is addressed by commonly-assigned U.S. Pat. No. 6,113,656 to Kimbrell which discloses a method for improving the dyeing of fabric treated with the Farmer chemistry. In addition, the structure of the amines disclosed by Farmer, especially those preferred by Farmer, can lead to chemical handling issues in textile finishing facilities (as will be discussed further herein) and also to quality issues resulting from attempting to handle such chemicals. Furthermore, it has proven difficult to control the batch to batch variation, within a somewhat narrow range, on certain styles, which in turn, leads to significant treated yardage that is not acceptable, either due to poor pilling performance or excessive strength loss.
More specifically, Farmer describes in U.S. Pat. No. 4,103,051 that organic amines are a particularly preferred class of compounds for this type of reaction, resulting in generally good control of the degree of pilling improvement obtained. Farmer discloses the use of aliphatic amines containing at least 10 carbon atoms. In addition, Farmer states that fatty diamines such as n-coco-1,3-propanediamine, are the preferred amines for this process.
It has been found that the use of the above-mentioned fatty diamines can impart detrimental variability to the textiles treated by this process. First these fatty diamines, especially those containing greater than 10 carbon atoms, tend to solidify at or around room temperature. This necessitates special storage and handling requirements in a typical textile dyeing operation such as, for example, drum heaters or other heating equipment to maintain the amine at a temperature above its melting point. Second, these compounds, such as the n-coco-1,3-propanediamine preferred by Farmer, are mixtures of unbranched carbon chains containing from 8 to 18 carbon atoms. This mixture tends to separate according to the size of the carbon chain resulting in unacceptable variations of the chemical composition and the degree of strength reduction obtained by this process. This again leads to special chemical handling requirements to minimize this potential variable, such as the use of drum mixers. Finally such diamines are known to adsorb and react with carbon dioxide from the air, resulting in an insoluble carbamate that does not react with polyester or other hydrolizable polymers. Without special attention to controlling the exposure of these amines to the air, various mixtures of products result. The net result can be less than the necessary amount of active amine being used to obtain the required strength reduction necessary to achieve good pilling performance. All of these potential chemical variations result in a process that can be very difficult to control within acceptable product performance tolerances.